To cope with the daily increase of electricity demands, smart grids are developed and implemented all over the world. In general, smart grids are a form of electricity networks, which utilize communications technologies (e.g. digital, wired and/or wireless etc.) and deliver electricity from suppliers to consumers or users by use of two-way communications to control the delivery and consumption of electricity. Compared to traditional grids, besides the delivery of electricity from suppliers to consumers or users, the smart grids also transmit information by use of the two-way communications for cost reduction, for balancing the electricity production and/or delivery with electricity consumption and/or for increasing reliability and transparency of electricity production, delivery and consumption. Advanced Metering Infrastructure (AMI) refers to systems, which measure, collect and analyze electricity usage, and interact with advanced devices, such as electricity meters etc., through various communications media, devices, systems etc. either on request (on-demand) or on pre-defined schedules. AMI is utilized also as an information gateway from utility to end users.
With the development of smart grids, also developments of new applications have become important. The applications are often incorporated in an information network, which is placed on the top of the traditional electricity grid and enables awareness for both the electricity producer and/or deliverer side and the electricity consumer side. An example of such an application incorporated in an information network is demand response (DR), by which consumption of electricity is managed in response to supply conditions, for example, when available, generated electricity amount is smaller than the consumed electricity amount and vice versa when higher electricity consumption is permitted, or when electricity consumption reduction or increase is reasonable in response to electricity market prices. With the demand response mechanism, Utilities may initiate electricity consumption reduction or increase by electricity consumers for balancing the provided/generated electricity amount and the consumed electricity amount. To this, when demand response mechanism is used, a corresponding request for changing the electricity consumption is transmitted from the utilities to electricity consumers or to electricity consuming systems or devices, respectively. In general, the demand response mechanism is well known and will, therefore, not be explained in more detail. For more information concerning smart grids and applications it is referred exemplary to “The Smart Grid in 2010: Market Segments Applications and Industrial Players”, LEEDS, D. J. (2009), GREENTECH MEDIA INC.
An example of communicating between a utility side and an electricity consuming side is provided in U.S. Pat. No. 7,747,537 B2, where the electricity consuming side is able to shed one or more loads in response to a load shed command from the utility side. Modern networked lighting system as an electricity load can vary their electricity consumption via dimming the lighting devices in the system. This gives the possibility to use the demand response mechanism for controlling electricity consumption or power consumption, respectively, in a lighting system.
In a lighting system, (some) lighting devices and/or lighting device groups can be dimmed towards a certain level to reduce their load. This may depend on functions and/or on characteristics of the lighting devices and/or lighting device groups. Therefore, load shedding capabilities of each lighting device and/or lighting device group are different.
The known control mechanisms for controlling the electricity consumption or power consumption, respectively, still fail to distribute the electricity or power consumption or load in the entire lighting system such: that an optimal illuminating is achieved by the lighting devices in the lighting system by considering the functions and/or on characteristics of the lighting devices and/or lighting device groups; that end user comfort is not sacrificed at the lowest level; that the impact of the dimming is not minimized to the function of the system.